A non-volatile memory device with a floating gate is capable of electrically programming and erasing data. In addition, a non-volatile memory device does not lose programmed data when power is cut off. A non-volatile memory device with a floating gate performs programming or erasing operations by injecting electrons into an electrically insulated floating gate or ejecting electrons from the floating gate. Electrons penetrate an insulation layer interposed between the floating gate and a semiconductor substrate either by hot carrier injection or Fowler-Nordheim tunneling (FN tunneling). Generally, a non-volatile memory device with a floating gate injects electrons into the floating gate or ejects electrons from the floating gate depending on a voltage of the floating gate driven by an operation voltage (i.e., a program voltage or an erasing voltage) that is applied to a control gate electrode located over the floating gate.
As semiconductor devices become highly integrated, a low operating voltage and a short line width is required. Thus, coupling ratio between the floating gate and the control gate electrode becomes an important factor in raising capacitance, which in turn reduces the operation voltage of the memory device. Coupling ratio means a ratio of the operation voltage of the control gate electrode to the voltage of the floating gate. If the coupling ratio increases, the voltage driven to the floating gate also increases with respect to the operation voltage of the control gate electrode. Therefore, the operation voltage of the non-volatile memory device with the floating gate can be decreased. Meanwhile, the coupling ratio increases as the capacitance between the floating gate and the control gate increases. Recently, various methods have been provided to raise the capacitance between the floating gate and the control gate electrode.